Masonry products, such as blocks or bricks for constructing walls, have been made for many years by molding processes. A typical molding process involves the use of what is commonly known as a static block-making machine. Pallets made from metal or wood are fed by a conveyor into the block-making machine, which generally comprises a mold, a stripping device, a vibration mechanism, and a device for filling the mold with a cementitious mix. After the pallet has been located, the mold is lowered onto the pallet to form a mold cavity defined by the upper surface of the pallet and the inside surfaces of the side walls of the mold. A cementitious mix is then introduced into the mold cavity through the open top of the mold while simultaneously vibrating the mold and/or pallet. A compression or compacting head is lowered onto the cementitious material in the mold to facilitate densification of the cementitious material. The molded cementitious material is then stripped from the mold by raising the mold while the compacting head remains stationary relative to the mold, thereby pushing the molded block through the open bottom of the mold.
It is common to split off a portion of the cured block, such as with a splitting machine or a hammer and chisel, so as to create a decorative face on a surface of the block that resembles the surface texture of natural stone. The face created by the splitting process is often referred to in the industry as “split face” or “rock face.” The splitting of cured blocks, however, involves additional equipment and manufacturing steps and results in material wastage. In order to avoid the shortcomings of conventional splitting processes, there have been efforts to achieve the same “split face” texture without additional splitting steps.
There are a number of patents, which disclose methods and apparatuses for producing a roughened surface on an uncured block during the molding process. For example, U.S. Pat. No. 3,981,953 to Haines is understood to disclose a method of forming a roughened block face in which cementitious material is placed in a mold cavity, with a grid-like series of elements being disposed in the cavity and suspended from a top plate. After the block material is compacted into the cavity, the side walls and top plate are drawn off the molded but uncured block. Upward movement of the top plate lifts the grid-like series of elements, and the block material between the elements and the lower plate is broken off from the lower block material in the mold, forming a roughened texture on the top face of the block. A drawback to this arrangement is that the pattern of the elements is cast in the top face of the block.
U.S. Pat. No. 3,940,229 to Hutton is understood to disclose a mold in which a small lip is formed on the inner, lower edge of a vertical wall of the mold. As the densified, composite material is stripped from the mold, the lip moves vertically up an adjacent side wall of the block, and tears some of the composite material away from the surface of the block. The lip temporarily retains this composite material in place against a portion of the mold wall as the mold is stripped. The retained material is thus dragged, or rolled, up the surface of the adjacent side wall of the block as the mold is stripped, creating a roughened texture on the side wall of the block.
The process of the '229 patent tends to produce a textured face having horizontal striations so as to provide what may be referred to as a “shingled” appearance. In addition, the textured face is slightly tapered or sloped, as a result of the lip retaining fill material as the mold is stripped from the block.
Another example of an alternative to splitting is shown in U.S. Pat. Nos. 5,078,940 and 5,217,630 to Sayles. These patents are understood to disclose a mold having a lower lip on a vertical wall of the mold, similar to that shown in the '229 patent. In addition, the mold employs a plurality of projections on the vertical wall above the lip, and a vertically oriented reinforcing mesh above the lip and spaced from the projections. When the mold is initially filled, the cementitious material fills in between the mesh and the wall, and around the projections. The combination of the lip, mesh and projections holds a large mass of compacted material against the mold as the mold is moved vertically upward to strip the uncured block from the mold. These patents appear to show the retained mass of material shearing from the rest of the material, and thus creating a roughened face on the molded block.
In the process of the '940 and '630 patents, the use of the projections holds a much larger mass of material against the mold side wall than is the case in the '229 process, and does this in a fashion so as to retain that material in the mold from cycle to cycle. Consequently, frequent stoppages in production may be required to clean the mold of material accumulated between the projections. Further, cleaning of the mold may be complicated by the presence of the screen.
Yet another apparatus for producing a block with a roughened surface is shown in U.S. Pat. Nos. 5,879,603 and 6,138,983 to Sievert. The '603 and '983 patents are understood to disclose a mold having generally parallel upper and lower lips on a vertical wall of the mold. As the mold is moved vertically to strip the uncured block from the mold, fill material is retained in the space between the upper and lower lips. Like the process of the '940 and the '630 patents, the retained material is sheared from the uncured block, thereby creating a roughened surface.
U.S. Pat. No. 6,209,848 to Bolles discloses an apparatus that is similar to the apparatus of the '603 and '983 patents. The '848 patent discloses a mold in which a lip is formed along the bottom edge of at least one wall of the mold, wherein a series of grooves are formed along the length of the lip.
Finally, U.S. Pat. Nos. 6,113,379 and 6,224,815 to LaCroix are understood to disclose a mold having two mold cavities separated by a metal grate. The grate has openings to permit fill material to flow through the openings and form a single molded article in the mold. When the molded article is discharged from the mold, the article is separated into two masonry units by the grate, with each masonry unit having a roughened surface where the units were previously joined.
Despite the foregoing processes, there exists a continuing need for new and improved methods and apparatus for producing a masonry block that does not involve splitting but which creates a textured surface that resembles the “split face” look that can be achieved with a conventional splitting process.